Ensure handlers have proper parent (#39426)

* Ensure role handlers are parented correctly. Fixes #36518

* Add delegate_to test for include_role handlers

test/integration/targets/include_import/roles/delegated_handler/handlers/main.yml

@@ -0,0 +1,4 @@
+- name: delegated assert handler
+  assert:
+    that:
+      - ansible_delegated_vars is defined

test/integration/targets/include_import/roles/delegated_handler/tasks/main.yml

@@ -0,0 +1,3 @@
+- command: "true"
+  notify:
+    - delegated assert handler